Recently, the TCP/IP is widely used in various computer communications as a result of a world-wide spread of the Internet. However, a great many users, who use a communication facility of the TCP/IP, do not have sufficient knowledge of details of a communication processing in the TCP/IP.
Herein, the TCP (Transmission Control Protocol) is a connection-oriented transmission control protocol for a transport layer and the IP (Internet Protocol) is a connectionless packet transfer protocol for a network layer. TCP and IP are major protocols used in the Internet.
In communication based on the TCP/IP, data throughput decreases when a loss of a packet occurs because of a congestion or a transmission error in a network, or when a parameter value such as a socket buffer size is different in two communication systems. In such cases, it is necessary to determine the cause of decreased throughput by analyzing details of the communication.
For inspecting a cause of decreasing throughput or, a protocol monitor is used to analyze a PDU (Protocol Data Unit) format and to display a result of the anaylsis. Further, an expert, who has a thorough knowledge of the details of the communication processing in the TCP/IP, analyzes a communication sequence by reading the result of the PDU format analysis.
The expert is necessary because the protocol monitor on the market does not have a function for analyzing a communication sequence and a function for inspecting a cause of throughput decreasing, while the protocol monitor has only a function for analyzing a PDU format and a function for displaying its result.
Therefor, it is difficult for the user who uses a communication facility of the TCP/IP to investigate a cause of decreasing throughput.